The invention relates to a method for reconstructing old underground pipes, wherein a breaking or cutting tool connected with a drive or a pipe section is moved through the old pipe from a starting shaft to a destination shaft or machine shaft, or from a starting ditch to a destination ditch or a machine ditch.
The state of the art is replete with static methods for trench-less reconstruction and/or replacement of pipes buried underground. In one of these methods, a spitting tool is pulled through the old pipe for replacing the pipe while retaining the original routing. The spitting tool is used to fragment, for example comminute, the old pipe and if necessary, to simultaneously widen the resulting underground bore hole which receives the fragments from the old pipe.
Such systems are described, for example, in the German Patents 196 08 980 C2 and 198 17 873 C2; they consist essentially of a sled which can be moved on a carriage by a hydraulic cylinder piston drive. The sled is includes latches which are configured to engage during a forward stroke of the hydraulic cylinder with rungs of a ladder framework consisting of individual segments. A breaking or cutting tool for demolishing the old pipe can be arranged at the free end of the ladder framework and used for simultaneously widening the created underground bore hole and/or for pulling in a new pipe section.
Drive units of this type have met with overwhelming success; however, they require a machine shaft or a machine ditch having dimensions commensurate with the dimensions of the drive unit and must leave sufficient space at the rear of the system so that a corresponding rod section can be coupled to the end of the rod assembly which protrudes from the rear end of the system. For example, when replacing old pressure and drainage pipe between a typical drainage or inspection shaft and the immediately adjacent shaft having a standard a diameter of only 100 cm, the drive unit occupies considerable space of the unobstructed shaft cross-section, which is then no longer available for the required work, for example for handling the rod sections and attaching the rod sections to the end of the rod assembly.
Moreover, time-consuming and expensive removal of the so-called channel from the shaft is required in order to provide the space for inserting and positioning the drive unit. The channel is approximately U-shaped in cross-section and is frequency tiled. The channel is aligned with the opposing openings at the pipe ends, and is used to direct the drainage water through the shaft.
Due to their space requirements, even short drive units cause space problems when coupling the rod sections to the rod assembly and connecting them to the rear end of the run to withstand push and pull forces. The length of the rod sections is therefore limited to approximately 50 cm. In addition, even short drive units cannot be used in a shaft, where the extension of the old pipe axis is not substantially aligned with the shaft diameter or runs through the shaft axis, but rather intersects the shaft as a secant, because miniaturization has limits due to design constraints and in view of the required large drive power.
When replacing a pipe from one ditch to the next, the space problems can be solved by enlarging the ditches. However, this requires commensurate soil excavation resulting in additional costs for labor, machines, transport and storage for the excavated soil.
The same problems associated with pipe replacement also occur in pipe reconstruction, where a new pipe made of individual pipe sections is pulled trough the old pipe, with tight clearance to the wall of the old pipe, wherein the length of the new pipe sections corresponds approximately to that of the rod sections.